Cleaning apparatus for oil well production

ABSTRACT

An apparatus for processing production fluid from an oil well in the field to obtain clean power oil for a fluid operated pump in the well. The apparatus is intended to service a single well, or at most a few wells, and includes components, including a tanktype separator, for removing solids, gas and water from the production fluid to obtain the clean power oil, which is pressurized by a triplex pump and delivered to the fluid operated pump in the well. The apparatus also includes a tank, either a separate storage tank, or a large separator tank, containing a sufficient reserve of power oil for running the fluid operated pump into and out of the well. A circulating pump having a capacity at least about twice that of the triplex pump continuously circulates the oil to be cleaned through one or more cyclones which continuously remove any solids. If desired, this apparatus can be used to furnish clean power water to the triplex, instead of oil.

United States Patent 1191 Mecusker l Apr. 9, 1974 CLEANING APPARATUS FOROIL WELL PRODUCTION Primary ExaminerJames A. Leppink [75] inventor:Mathew Mecusker La Habra, Attorney, Agent, or FirmHarris, Kern, Wallen &

C lif Tinsley [73] Assignee: Kobe, lnc., Huntington Park, Calif. 22Filed: June 22, 1973 [57] ABSTRACT An apparatus for processingproduction fluid from an [21] Appl' 372'533 oil well in the field toobtain clean power oil for a fluid R l t d Us, A i i D m operated pumpin the well. The apparatus is intended [63] Continuatiomimpan of No. 25687L May 25 to service a single well, or at most a few wells, and in-1972,15, 4,917,655 I eludes components, including a tank-type separator,

for removing solids, gas and water from the produc- 521 vs. c1. 166/75tioh fluid to Obtain the clean P Oil, which is P 51 1111. C1 E211133/03, E21b 43/00 smiled by a triplex P and delivered IO the fluid 58Field 61 Search, 166/75, 267; 210/73, 512 Operated P in t The apparatusalso v cludes a tank, either a separate storage tank, or a large 5References Cited separator tank, containing a sufficient reserve ofUNITED STATESPATENTS power oil for running the fluid operated pump intoand out of the well. A circulating pump having 21 ca- 1,433,956 10/1922Knox 166/267 p i y at least abouttwice that of h triplex p p gigg' j lcontinuously circulates the oil to be cleaned through 276585O 10/1956Allen one or more cyclones which continuously remove any 1 33 5/1936McKee 166/267 solids. If desired, this apparatus can be used tofurnish3,254,711 6/1966 Parker ..166 75 Clean Power Water to the triplex,instead of 3,3l0,l09 3/1967 Marx et a1. 166/75 I 1 1973 Palmour 166/68 7(331M515 Drawmg Flgul'es- T2 /PLE)C PUMP iEP/Q 3.802.501 SHEET 1 0F 3PATENTED APR 9 i974 CLEANING APPARATUS FOR OIL WELL PRODUCTION CROSSREFERENCE TO RELATED APPLICATION This application is acontinuation-in-part of my copending application Ser. No. 256,871, filedMay 25, 1972, now US. Pat. No'. 4,917,655, issued Sept. 18, 1973.

- BACKGROUND OF INVENTION.

SUMMARY AND OBJECTS OF INvENTIoN The primary object of the presentinvention is to provide a self contained apparatus which may beinstalled at or adjacent the well head to obtain the necessary cleanpower liquid from the production fluid as the latter is produced.

Another object of the invention is to provide an apparatus havingcomponents for removing at least solids and gas from the productionfluid to obtain clean power liquid for the fluid operated pump in thewell,

the clean power liquid being pressurized for delivery to the fluidoperated pump by a triplex pump forming part of the unit.

Another object is to provide an apparatus having a storage capacitysufficient for such related operations as circulating the fluid operatedpump into and out of the well.

A further object is to continuously circulate previously cleaned powerliquid, through a cyclone or cyclones to remove solids.

The invention may be summarized as including, and an important object isto provide an apparatus which includes: a production fluid inlet forproduction fluid from the well; a production fluid outlet connectible toa point of production fluid disposal; a power liquid outlet connectibleto the liquid operated pump in the well; a separator connected to theproduction fluid inlet, the separator having at the top and'bottomthereof upper and lower outlets connected to the production fluid outletand having an intermediate outlet; a cyclone having a liquid inlet and aliquid outlet and having a solids outlet, the latter being connected tothe production fluid outlet; a circulating pump having an inletconnected to the intermediate outlet of the separator, and having anoutlet connected to the liquid inlet of the cyclone; a triplex pump, orequivalent, having an inlet connected to the liquid outlet of thecyclone, and having an outlet connected to the power liquid outlet; thecirculating pump having a capacity in excess of that of the triplexpump; and a bypass from the liquid outlet of the cycloneback to theinlet of the circulating pump;

A further object is to provide an apparatus of the foregoing naturewherein the circulating pump has a capacity considerably in excess ofthat of the triplex, and preferably at least twice the tiplex capacity,and wherein there is a bypass from the clean liquid outlet of thecyclone back to the circulating pump inlet. With this construction, thepower liquid being cleaned is continuously circulated through thecyclone for further solids removal.

Other objects in connection with various embodiments are to provide anapparatus wherein the bypass conveys the liquid from the liquid outletof the cyclone directly back to the inlet of the circulating pump, or byway of the separator, or by way of a separate storage tank. An object inconnection with another embodiment is to connect the circulating pumpinlet to the intermediate'separator outlet through the storage tankmentioned.

Another object in connection with one embodiment is to provide aprimarycyclone for precle'aning the fluid delivered to the separator,undesirable materials discharged by this primary cyclone being deliveredto the production fluid outlet of the apparatus.

The foregoing objects, advantages, features and results of the presentinvention, together with various other objects, advantages, features andresults which will be evident to those skilled in the oil wellproduction fluid'cleaning art in the light of this disclosure, may

be achieved with the exemplary embodiments of the invention illustratedin the accompanying drawings and described in detail hereinafter.

DESCRIPTION OF DRAWINGS In the drawings: FIG. 1 is a schematic viewof anoil well production fluid cleaning apparatus which embodies theinvention;

FIG. 4 is a sectional-perspective view of a secondary cycloneincorporated in the apparatus of FIG. 1 of the drawings; and I FIG. 5 isa view similar to FIG. 1, but showing a simpler and presently preferredembodiment of the invention.

DESCRIPTION OF EXEMPLARY EMBODIMENT or INVENTION, FIGS. 1 To 4 Referringinitially to FIG. 1 of the drawings, the oil well production fluidcleaning apparatus of theinvention is illustrated thereindiagrammatically and is composed of components which, for the most part,are entirely conventional so that detailed descriptions of thecomponents are not necessary, the invention residing in the combinationof these components and the relationship between them.

Throughout FIG. 1 there are legends indicating such things as flow ratesin barrels per day, pressures in pounds per square inch, and the like.These are illustrative only and serve to indicate flow rates andpressures which will provide an operative system. It will be understood,of course, that other flow rates and pressures may be substituted. Also,throughout FIG. 1 there are various conventional components which areidentified by the legends BPR (pressure reducing valve) and RV (reliefvalve). It is thought that the fuctions of these conventional componentswill be apparent so that descriptions thereof are not necessary.

Considering the cleaning apparatus generally, it includes a productionfluid inlet 12 which receives the production fluid pumped from an oilwell, not shown, by a conventional fluid operated pump, not shown. Theproduction fluid may include native well fluid and spent power oil (orwater) discharged by the pump. The cleaning apparatus also includes aproduction fluid outlet 14 which is shown as comprising a lease lineleading to a suitable point of disposal for the production fluid, suchas processing equipment, storage tanks, and the like. The apparatus alsoincludes a power oil (or 'water) outlet 16 which is connectible to thefluid operated pump in the well and from which the fluid operated pumpis supplied with clean power oil furnished by the apparatus.

As is well known, the production fluid from the well entering thecleaning apparatus at the production fluid inlet 12 may contain oil,water, gas, solids, and the like.

The function of the apparatus is to remove substantially all of the gas,water, solids, and other contaminants, from the crude oil so as toprovide the desired clean operating fluid for the pump in the wall. Thecontaminants, i.e., the gas, water, solids, and the like, are dischargedfrom the apparatus at the production fluid outlet 14'.

The production fluid flowing into the cleaning apparatus at the inlet 12enters the inlet 18 of a primary cyclone 20 which is illustrateddiagrammatically in FIGS. 2 and 3. The primary cyclone 20 is providedwith a gas outlet 22 and a solids and dirty liquid outlet 24 which areconnected to the production fluid outlet 14 by lines 26 and 28 and aline 30. The primary cyclone 20 differs from the usual cyclone in thatit is provided at the top with an extra cylindrical section 32 connectedto the lower section by a central duct 34. Liquid is discharged from thecylindrical section 32 tangentially through a clean liquid outlet 36.

With the foregoing construction, major portions of the gas and solidsare removed so that the fluid discharged through the outlet 36 of theprimary cyclone 20 consists of oil and water which are relatively gasand solids free.

The clean fluid from the outlet 36 enters the inlet 38 of a conventionalthree-phase separator 40. The flow into the separator 40 is controlledby a float actuated valve 42 the float of which is in a storage tank 56to be described. The separator 40 is provided with gas and water outlets44 and 46 connected to a line 48 leading to the production fluid outlet14. The water level in the separator 40 is controlled by a floatactuated valve 50 controlling flow through the water outlet 46, thefloat of the valve 50 being in the separator. The oil phase leaves theseparator 40 through a clean oil outlet 52 connected to the inlet 54 ofa clean oil storage tank 56, the liquid level in the storage tank beingcontrolled by the float actuated valve 42. The oil level in theseparator 40 is controlled by a float actuated valve 58 the float ofwhich is in the separator,

The foregoing combination of the primary cyclone 20 and the three-phaseseparator 40 is one of the important features of this embodiment of theinvention. The primary cyclone 20 disposes of most of the dirty liquidand the gas, discharging only relatively clean liquid into the separator40. Also, the primary cyclone 20 achieves some degree of oil and waterseparation so that the water content of the oil entering the separator40 is reduced. This results in a substantial reduction in the load onthe separator 40, which means that the separator can operate much moreeffectively for a given capacity.

The storage tank 56 provides a reserve of clean power oil whenever theseparator 40 runs out of oil due to a gas head from the well, or suchwell servicing operations as pumping the fluid operated pump in or out.The storage tank 56 has a power oil outlet 60 which is connected to theinlet of'a circulating pump 62 having an outlet connected to the inlets64 of three parallel connected, secondary cyclones 66. One of these isshown in some detail in FIG. 4, which also illustrates itscharacteristic mode of operation. The secondary cyclones 66 are providedat their lower ends with solids outlets 68 connected by a line 71 to theline 30 leading to the production fluid outlet 14.

The secondary cyclones 66 are provided at their upper, ends with cleanpower oil outlets connected to a line 72 leading to the inlet of aconventional triplex pump 74. The clean power oil outlets 70 of thesecondary cyclones 66 are also connected to a bypass line 76 leadingback to the storage tank inlet 54.

The outlet of the triplex 74 leads to a pressure controller 78 whichdetermines the power oil pressure delivered to the power oil outlet 16leading to the fluid operated pump in the well. Any excess power oilfrom the pressure controller 78 is returned to the storage tank 56 by aline 80 connected to the bypass line 76.

An important feature of all embodiments of the invention is that thecapacity of the circulating pump 62 and the combined capacities of thesecondary cyclones 66 are considerably greater than, and preferably atleast about twice, the capacity of the triplex 74. Consequently,assuming, for example, a flow of 5,000 barrels per day through thesecondary cyclones 66 and an output of 2,500 barrels per day by thetriplex 74, 2,500 barrels of oil are returned to the storage tank 56daily for further processing in the secondary cyclones, the storage tankcomprising part of a bypass from the cyclone outlets 70 back to theinlet of the circulating pump 62. This constant recirculation of part ofthe clean power oil in the storage tank 56 through the secondarycyclones 66 results in the removal of further foreign matter from thepower oil, thereby minimizing any residual foreign matter in the poweroil delivered to the triplex 74, and ultimately to the fluid operatedpump in the well. Thus, the storage tank 56 serves the additionalfunction of permitting recirculation of the power oil through thesecondary cyclones 66 for further cleaning, which is an importantfeature.

Another feature resides in the use of the parallel connected secondarycyclones 66, instead of a single larger cyclone. The smaller cyclonespermit developing higher centrifugal forces, and thus better separationof contaminants.

DESCRIPTION OF EXEMPLARY EMBODIMENT, FIG. 5

Turning now to FIG. 5 of the drawings, this embodiment of the oil wellproduction fluid cleaning apparatus of the invention is illustratedtherein diagrammatically and is generally similar to the embodiment ofFIGS. 1

. to 4. The embodiment of FIG. 5 is composed of compo-- nents which areconventional so that detailed descriptions of the individual componentsare not necessary, the invention again, as in the previous embodiment,residing in the combination of these components and the relationshipbetween them.

Throughout FIG. 5, there are legends indicating exemplary flow rates inbarrels per day. These are illustrative only and serve to indicate flowrates which will provide an operative system. It will be understood, ofcourse, that other flow rates may be substituted. Also, throughout FIG.5, there are various conventional components which are identified bylegends clearly indicating their functions so that further descriptionswill not be necessary.

In addition, since many of the components of the cleaning apparatus ofFIG. 5 correspond to components of the embodiment of FIGS. 1 to 4, thecomponents of FIG. 5 will be identified by reference numerals higher byone hundred than those used for the corresponding components of FIGS. 1to 4.

The apparatus of FIG. 5, considered generally, includes a productionfluid inlet 112 which receives the production fluid pumped from an oilwell, not shown, by a conventional bottom hole, fluid operated pump, notshown, in the well. The production fluid may include native well fluidand spent power oil (or water) discharged by the pump. 1 I Theapparatus'of FIG. 5 also includes a production fluid outlet 114 which isshown as comprising a lease line 115. leading to a suitable point ofdisposal for the production fluid, such as processing equipment, storagetanks, and the like. The apparatus also includes a power oil (or water)outlet 116 which is connectible to the fluid operated pump in the welland from which the fluid operated pump is supplied with clean powerliquid furnished by the apparatus.

As is well known, the production fluid from the well entering thecleaning apparatus at the production fluid inlet 112 may contain oil,water, gas, solids, and the like. Thefunction of the apparatus is toremove substantially all of the gas, solids, and other contaminants,

6 with the lower intermediate outlet 150 is normally closed, and may beopened, in any suitable manner, to

' provideadditional liquid to the circulating pump 162,

ratus at the inlet 112 flows through a line 118 into a three phaseseparator or separator tank 140. The liquid level in the separator 140is controlled by a float actuated valve 142 in the lease line 1 15, thefloat for actuat-- ing this valve being identified by the numeral 143and being located in the separator.

.The separator 140 is provided with upper and lower gas and wateroutlets 144 and 146 both connected to the lease line 115, the formerthrough a pressure controller and the latter through a line 147.

The separator 140 is provided with upperand lower power fluid outlets148 and 150 which are intermediate outlets, i.e., which are below theupper outlet 144 and above the lower outlet 146. The upper and lowerpower fluid outlets I48 and 150 are connected to parallel valves 152 and154 both connected to the inlet 156 of a circulating pump 162. The valve152 connected to the upper intermediate outlet 148 is normally open, andnormally connects the oil zone of the separator 140 to the circulatingpump 162. The valve 154 associated if necessary, for performing suchfunctions as circulating the bottom hole, fluid operated pump into orout of the well. (While the power fluid outlets 148 and are shown asnormally communicating with the oil zone of the separator 140, it willbe understood that they may communicate with the water zone'thereof. Forexample, in a well having a very high water cut, it may be necessary touse water as the power fluid,or as the fluid for circulating the bottomhole pump into or out of the well, or both.)

The outlet 163 of the circulating pumpi162 is connected through a line164 and a meter 165 to the inlet 167 of a cyclone 166 similar to one ofthe cyclones 66.

If desired, there may be two or more of the cyclones 166 connected inparallel in the same manner as the cyclones 66.

The cyclone 166 is provided at its upper end with a clean power fluidoutlet 170 leading through-a line 171 and a line 172 to the inlet of atriplex, or equivalent, 174, the outlet of the latter being connected tothe power fluid outlet 116. The cyclone 166 is also provided with alower outlet 175, for solids-contaminated liquid, connected through amanual valve 176 and a meter 177 to the lease line 115, Le, theproduction fluid outlet 114. v A chemical pump 178 may, if desired, beprovided to inject suitable conditioning chemicals into the line 172through a line 179 and into the line from the well to the separator 140through a line 180.

The outlet 170 of the cyclone 166, in addition to being connected to theinlet of the triplex 174, is connected back to the inlet of thecirculating pump 162 through a line 181 containing a manual valve 182,which valve may be adjusted to control the relative amounts of powerfluid which are delivered to the triplex 174 and returned back to theinlet of the circulating pump 162. Any excess power fluid discharged bythe triplex 174 is returned from the power fluid outlet 116-back to theproduction fluid inlet 112 through a pressure controller, which. governsthe power fluid pressure delivered to the bottom hole pump.

The outlet 170 of the cyclone 166 is also connected through a checkvalve 184 and a manual valve 186 to the production fluid inlet of theseparator 140. Thus, that portion of the clean power fluid discharged bythe cyclone 166 which is not delivered to the triplex 174, can bereturned to the circulating pump inlet 156, or the separator 140, orboth depending upon the settings of the manual valves 182 and 18.6. Thecapacity of the circulating pump 162 is considerably greater than thatof the triplex 174, preferably'by a factor of two or more. With theparticular illustrative legends applied to FIG. 5, the capacity of thecirculating pump is 4,500

barrels per day while the capacity of the triplex 174 is 1,000 barrelsper day, which means that, with this illustrative example,-3,500 barrelsper day are recirculated from the cyclone outlet 170 to the circulatingpump inlet 156, either directly by the line 181, or indirectly throughthe separator 140, or both. depending upon the settings of the manualvalves 182 and 186.

If all of the recirculated liquid is returned from the cyclone 166directly to the circulating pump 162, it is continuously cleaned by thecyclone to insure a continuous supply of power liquid for the triplex174 which has been repeatedly cleaned, this being an important feature.Alternatively, the excess cleaned power liquid discharged by the cyclone166 may be recirculated by way of the separator 140 to build up in theseparator a reserve supply of at least partially cleaned power liquidwhich is subjected to a final cleaning in the cyclone 166 before beingdelivered to the triplex 174. Alternatively, a combination of these twoprocedures may be used by having both valves 182 and 186 at leastpartially open.

The flow could be in either direction in the line 147. The normal flowcould be 250 B/D out of the cyclone 166, as shown in FIG. 5. However, itmight be that the underflow from the cyclone 166 is 550 B/D and, thus,50 B/D would recycle back into the tank 140 through the line 147. Theunderflow at 175 is regulated by the throttling valves 182 (or 186) and176.

Thus, the cleaning apparatus of FIG. is a very versatile one which canbe used in a number of different ways, as hereinbefore outlined.Further, the embodiment currently under consideration is simpler thanthat previously described in that it eliminates the upstream cyclone 20and the separate storage tank 56, the tank of the separator 140 beingmade sufficiently large to maintain an adequate reserve supply of powerliquid.

Although exemplary embodiments of the invention have been disclosed forpurposes of illustration, it will be understood that various changes,modifications and substitutions may be incorporated in such embodimentswithout departing from the spirit of the invention as defined by theclaims appearing hereinafter.

I claim as my invention:

1. An apparatus for processing production fluid from an oil well in thefield to obtain clean power liquid for a liquid operated pump in thewell, including:

a. a production fluid inlet for production fluid from the well;

b. a production fluid outlet connectible to a point of production fluiddisposal;

c. a power liquid outlet connectible to the liquid operated pump in thewell;

d. a separator connected to said production fluid inlet, said separatorhaving at the top and bottom thereof upper and lower outlets connectedto said production fluid outlet and having an intermediate outlet;

e. a cyclone having a liquid inlet and a liquid outlet and having asolids outlet, the latter being connected to said production fluidoutlet;

f. a circulating pump having an inlet connected to said intermediateoutlet of said separator, and having an outlet connected to said liquidinlet of said cyclone;

g. a triplex pump having an inlet connected to said liquid outlet ofsaid cyclone, and having an outlet connected to said power liquidoutlet;

h. saidcirculating pump having a capacity in excess of that of saidtriplex pump; and i i. a bypass from said liquid outlet of said cycloneback to said inlet of said circulating pump.

2. An apparatus according to claim 1 wherein said bypass includes saidseparator.

3. An apparatus as defined in claim 1 wherein said bypass leads fromsaid liquid outlet of said cyclone directly back to said inlet of saidcirculating pump.

4. An apparatus as set forth in claim 1 wherein said bypass includes astorage tank.

5. An apparatus according to claim 4 wherein said inlet of saidcirculating pump is connected to said intermediate outlet of saidseparator through said storage tank.

6. An apparatus as defined in claim 1 wherein there are upper and lowerintermediate outlets in vertically spaced relation between said upperand lower outlets and respectively connected to said circulating pumpinlet through parallel, upper, normally open, and lower, normallyclosed, valves.

7. An apparatus for processing production fluid from an oil well in thefield to obtain clean power liquid for a liquid operated pump in thewell, including:

a. a production fluid inlet for production fluid from the well;

b. a production fluid outlet connectible to a point of production fluiddisposal;

c. a power liquid outlet connectible to the liquid operated pump in thewell;

d. a separator connected to said production fluid inlet, said separatorhaving vertically spaced outlets connected to said production fluidoutlet and having another outlet;

e. a cyclone having a liquid inlet and a liquid outlet and having asolids outlet, the latter being connected to said production fluidoutlet;

f. a circulating pump having an inlet connected to said other outlet ofsaid separator, and having an outlet connected to said liquid inlet ofsaid cyclone;

back to said inlet of said circulating pump.

2723*? UNITED STATES PATENT OFFICE CERTIFICATE OF CURRECTION Patent No.3,802,501 Dated April 9. 1974 Inventor-(s) It is certified that errorappears in the above-identified patent I and that said Letters Patentare hereby corrected as shown below:

Page 1: Related 1.1.8. Application Data, [53],

."Pat. vNo. 4,917,655" should be --Pat. No. 3,759,324".

Column 1, line 9, "Pat. No. 4,917,655" should be --Pat. No. 3,759,324".

Column 2, line 4, "tiplex" should be --tri.plex--.

Column 3, line'2, "fuctions" should be "functions";

Column 3, line 26, "wall" should be -well-.--.

Signed and sealed this 1st day of October 1974.

(SEAL) Attest:

McCOY M. GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner ofPatents

1. An apparatus for processing production fluid from an oil well in thefield to obtain clean power liquid for a liquid operated pump in thewell, including: a. a production fluid inlet for production fluid fromthe well; b. a production fluid outlet connectible to a point ofproduction fluid disposal; c. a power liquid outlet connectible to theliquid operated pump in the well; d. a separator connected to saidproduction fluid inlet, said separator having at the top and bottomthereof upper and lower outlets connected to said production fluidoutlet and having an intermediate outlet; e. a cyclone having a liquidinlet and a liquid outlet and having a solids outlet, the latter beingconnected to said production fluid outlet; f. a circulating pump havingan inlet connected to said intermediate outlet of said separator, andhaving an outlet connected to said liquid inlet of said cyclone; g. atriplex pump having an inlet connected to said liquid outlet of saidcyclone, and having an outlet connected to said power liquid outlet; h.said circulating pump having a capacity in excess of that of saidtriplex pump; and i. a bypass from said liquid outlet of said cycloneback to said inlet of said circulating pump.
 2. An apparatus accordingto claim 1 wherein said bypass includes said separator.
 3. An apparatusas defined in claim 1 wherein said bypass leads from said liquid outletof said cyclone directly back to said inlet of said circulating pump. 4.An apparatus as set forth in claim 1 wherein said bypass includes astorage tank.
 5. An apparatus according to claim 4 wherein said inlet ofsaid circulating pump is connected to said intermediate outlet of saidseparator through said storage tank.
 6. An apparatus as defined in claim1 wherein there are upper and lower intermediate outlets in verticallyspaced relation between said upper and lower outlets and respectivelyconnected to said circulating pump inlet through parallel, upper,normally open, and lower, normally closed, valves.
 7. An apparatus forprocessing production fluid from an oil well in the field to obtainclean power liquid for a liquid operated pump in the well, including: a.a production fluid inlet for production fluid from the well; b. aproduction fluid outlet connectible to a point of production fluiddisposal; c. a power liquid outlet connectible to the liquid operatedpump in the well; d. a separator connected to said production fluidinlet, said separator having vertically spaced outlets connected to saidproduction fluid outlet and having another outlet; e. a cyclone having aliquid inlet and a liquid outlet and having a solids outlet, the latterbeing connected to said production fluid outlet; f. a circulating pumphaving an inlet connected to said other outlet of said separator, andhaving an outlet connected to said liquid inlet of said cyclone; g. atriplex pump having an inlet connected to said liquid outlet of saidcyclone, and having an outlet connected to said power liquid outlet; h.said circulating pump having a capacity in excess of that of saidtriplex pump; and i. a bypass from said liquid outlet of said cycloneback to said inlet of said circulating pump.